First point: it's not a cluster. It's a single server with massive amounts of cache (like 1Gbyte or more of the L3 cache) and optimized everything. When you l

First point: it's not a cluster. It's a single server with massive amounts of cache (like 1Gbyte or more of the L3 cache) and optimized everything. When you login via ssh to your server, each keypress creates an interrupt which is handled by the CPU. If you are using emacs , even on the terminal it might be multiple interrupts due to screen refresh etc. Mainframe: generate the form or the screen data. Send it. 1 interrupt. Your terminal or terminal program handles everything until you send 1 or more lines (not characters) back. A dedicated processor handles communication with the terminal. It then bundles up whatever the changes are and sends it to the CPU. 1 interrupt. Disk, network etc. is the same, with dedicated processors on the network card or disk controller that go out and send/retrieve the data without CPU intervention. Database table retrieval: the table is sent to the CPU, already sorted in the requested order. Etc etc.